The present invention relates to a machine for in particular grinding cylindrical surfaces which project from a body, and in particular trunnions of tripod elements for homokinetic joints, this machine being also applicable to other operations for machining cylindrical surfaces on workpieces comprising a body to which blanks of said surfaces are connected.
It is conventional to effect a center-less grinding of many workpieces, for example completely cylindrical workpieces such as the races of ball bearings, shafts, etc. For this purpose, the cylindrical surface to be rectified itself acts as a rotating support surface bearing against a supporting bar during the grinding operation.
On the other hand, this technique cannot be employed when the surface to be ground is too short to act as a support and is in overhanging relation on a body which does not have another coaxial cylindrical surface which could perform this function.
This is in particular the case of slidable tripod elements for homokinetic joints. Thus, since the introduction of tripod homokinetic joints in 1960 up to the present time, more than 100 millions of tripod elements have been ground between points by means of six centers previously machined in each blank of the tripod by means of a special machine, namely a center at the end of each trunnion and a center in confronting relation to the centers at the end of each trunnion in the hub or body.
For the purpose of permitting a center-less grinding, and more generally machining, of such workpieces, so as to economize the machining of the center, a machine has been proposed (patent G.B. Pat. No. 792,811) comprising a surface for supporting a reference surface for the body of the workpiece, and a device for fixing said body on said surface and releasing said body. However, in this known arrangement, it is difficult to precisely and rapidly position each workpiece to be machined on the support surface of the machine.